Arcelio J. Malcolm

Guaianolide-type sesquiterpene lactones of Montanoa tomentosa subsp. xanthiifolia and M. tomentosa subsp. rosei and the molecular structures of two pumilin analogs

Abstract Montanoa tomentosa subsp. xanthiifolia and M. tomentosa subsp. rosei produce guaianolides which are very similar to those previously reported from Berlandiera pumila, B. texana and B. lyatra . The molecular structures of 3α-epoxypumilin and 8-acetyl-9-desacylpumilin-9-methacrylate were determined by single crystal X-ray diffraction.

Longicornins A to D, four cis-1(10),cis-4-germacradienolides from Melampodium longicorne

Abstract The isolation and structure determination of four new cis -1(10), cis -4-germacradienolides, longicornins A–D, from Melampodium longicorne is described. The structure determinations involved NMR and mass spectral methods and chemical transformations. The molecular structure of longicornin A was determined by single crystal X-ray diffraction. The crystallographic data suggest revision at the chiral center C-9 of melcanthins A–G and also at C-2 in melcanthins B and C.

Sesquiterpene lactones of Montanoa guatemalensis and Montanoa tomentosa subsp. Xanthiifolia

Abstract New 4,5-epoxygermacra-12,6β-olides from Montanoa guatemalensis and a Guatemalan disjunct collection of M. tomentosa subsp. xanthiifolia are reported. These compounds were unlike those from the 10 other Mexican collections of M. tomentosa previous investigated.

Tomexanthin, an oxepane diterpene from montanoa tomentosa

Abstract Chemical analysis of Montanoa tomentosa yielded an oxepane diterpene, tomexanthin, which was characterized by spectral comparison with the previously established zoapatanol.

Germacra-12,6β-olides from Montanoa revealii and M. mollissima

Abstract Montanoa revealii and M. mollissima yielded a series of germacra-12,6β-olides similar to those previously reported from M. hibiscifolia and M. pteropoda.

Germacranolides from Melampodium americanum and Melampodium pilosum

Abstract Chemical analysis of Melampodium americanum yielded, besides the known melampodinin A, four new melampolides, melampodinin B, melampodinin C, 9-des

Melrosins A, B and C, three cis-1 (10)-cis-4-germacradienolides from Melampodium rosei☆

Abstract The isolation and structure elucidation of the three new cis -1(10)- cis -4-germacradienolides, melrosins A, B and C, from Melapodium rosei are reported. The structure determination involved chemical and spectral methods including 1 H NMR correlations with melrosin A the structure of which had been determined by single crystal X-ray diffraction.

The isolation and first X-ray crystal structure of two new germacra-cis-1(10), cis-4-dien-trans-6α, 12-olides from Melampodium

The structures of two new germacra-cis-1(10),cis-4-dien-trans-6α, 12-olides, longicornin A from Melampodium longicorne and melrosin A from M. rosei, have been determined by single crystal X-ray analysis; configurational revisions of the structurally related melcanthins A—G are suggested.

The molecular structures of two melampolides

The melampolide-class sesquiterpene lactone 11βH,13-dihydro-14-hydroxy-(1,10)-cis-parthenolide, C15H22O4, 1, crystallizes in orthorhombic space group P212121 with a = 7.435(2), b = 12.678(2), c = 14.991(2) Å, V = 1413.1(8) Å3 and Z = 4. The aldehyde analog, C15H20O4·H2O, 2, crystallizes as the monohydrate in orthorhombic space group P212121 with a = 9.061(2), b = 9.295(2), c = 17.761(4) Å, V = 1495.8(9) Å3, and Z = 4. The 10-membered rings of the two molecules adopt approximate chair-boat conformations. In both compounds, the double bond at C1=C10 position of the cyclodecene ring is Z, while the C4=C5 is epoxidized with an E-configuration. The C15 methyl is β and H5 is α. The lactone ring is trans fused at the C6 and C7 positions to the 10-membered ring. The C13 methyl group has an α orientation in both molecules.